1. Technical Field
The present invention relates to a cathode active material and a cathode for a lithium ion secondary battery, and the lithium ion secondary battery.
2. Background of the Invention
Patent Document 1 discloses a lithium transition metal oxide as a cathode active material in a lithium battery. This lithium transition metal oxide has a ratio of Li to the transition metal of 1.00 to 1.08.
A battery disclosed in Patent Document 2 uses a cathode and a separator to enhance elevated temperature properties, wherein the cathode comprises a cathode active material represented by the composition formula: LifCogNihMnjM1kO(2−m)X1n, wherein X1 is at least one selected from the group consisting F, Cl and Br, and each of f, g, h, j, k, m and n is a value in the range of 0.8≦f≦1.2, 0≦g≦1, 0<h≦1, 0≦j≦1, 0≦k≦0.1, g+h+j+k=1, −0.1≦m≦0.2, and 0≦n≦0.1, and the like, and the separator is impregnated with an electrolyte comprising a cyclic carbonic ester derivative having a halogen atom.
A lithium ion secondary battery disclosed in Patent Document 3 uses a cathode active material represented by the composition formula: LiaNi1−b−cM1bM2cO2 wherein 0.95≦a≦1.05, 0.01≦b≦0.10, 0.10≦c≦0.20, M1 is one or more elements selected from the group consisting of Al, B, Y, Ce, Ti, Sn, V, Ta, Nb, W and Mo, and M2 is one or more elements selected from the group consisting of Co, Mn and Fe. The Li content of this cathode active material is represented by “a” with the range of 0.95≦a≦1.05.